This invention relates generally to ventilation equipment and more particularly to a ridge vent having a damper which is opened and closed by temperature sensitive springs constructed of a shape-memory alloy.
Ridge vents have long been used to provide ventilation at ridges and other areas of the roofs of industrial, commercial, residential, institutional and other buildings. The type of ridge vent that is typically employed on industrial and commercial buildings includes a sheet metal housing equipped with a damper that serves as a valve to control the discharge of air through a ventilation passage. The damper is opened and closed by an actuator that is usually either a chain operated mechanism or an electric motor actuator. The actuator is operated to open the damper when it is desired to vent hot air from the ceiling area of the building and to close the damper when there is no need for ventilation.
This conventional ridge vent construction has several shortcomings which have detracted from its ability to reliably perform its intended function. Normally, it is necessary for someone to initiate the operation of the actuator, and this does not always occur at appropriate times. For example, the damper may be accidentally left open in cold weather so that heated air is able to escape in large quantities, thus increasing the heating requirements of the building. Conversely, the damper may not be opened when ventilation is necessary, and the ceiling area temperature may become excessive before it is recognized that the damper should be opened.
The various chain and motor actuators that have been used in the past are relatively costly and add significantly to the overall cost of the ridge vent. They also include a number of gears and other mechanical components that complicate the mechanism and are subject to the usual mechanical problems such as wear. Because of the inaccessible location of the ridge vent, mechanical breakdowns and other problems with the actuator are at best difficult to repair, and the actuator components are likewise difficult to inspect if they can be inspected at all.
Therefore, it is evident that a need exists for a ridge vent in which the damper actuator is simple, economical, reliable and automatic. It is the principal goal of the present invention to provide such an actuator.
More specifically, it is an important object of the invention to provide a ridge vent having a damper actuator that automatically opens and closes the damper at a selected temperature in order to ventilate when necessary and avoid undue escape of inside air when there is no need for ventilation. Among the other objects of the invention are to provide a damper actuator which is constructed simply and economically, which is devoid of mechanical parts that are subject to wear, and which operates reliably without the need for external power.
In accordance with the invention, the damper of a ridge vent is mounted on specially constructed coil springs which are formed from a shape-memory alloy. The shape-memory alloy is processed such that it exhibits temperature sensitive characteristics which cause the springs to be contracted at temperature levels below a selected temperature at which it is desired for the damper to close, and to expand when the temperature rises above the selected level. The damper is mounted on the springs, and the springs maintain the damper in its closed position when the springs are contracted and in its open position when the springs are expanded. Consequently, the damper automatically opens at temperatures above the selected temperature level and closes at lower temperatures.
The shape-memory alloy actuator is more economical than the actuators that have been used in the past to control the dampers of ridge vents, and it is much simpler. There is no need to make adjustments of the actuator after the ridge vent has been installed, and the actuator lacks mechanical parts that can wear out or otherwise malfunction. Spring fatigue is not a significant problem because chemical changes in the alloy rather than mechanical forces cause the springs to expand and contract. A particularly important advantage is the reliable automatic operation of the actuator in response to the sensed temperature.